The two processes that Rheticus links together have been known for a long time—and yet are quite new. Electrolysis, for example, has been used since the late 19th century for the industrial production of chlorine and sodium and potassium hydroxide solutions. In Rheticus, however, Siemens is pioneering the use of a CO2 electrolyzer in industrial application. In this device, water is oxidized to oxygen (O2) at the positive terminal (a titanium anode coated with iridium oxide) and hydrogen (H2) is also produced. CO2 is circulated around the negative terminal, a silver cathode, where part of the gas is reduced by the electric current to carbon monoxide (CO). The resulting product is a synthesis gas, a mixture of CO2, CO, and H2. The ratio of the components is determined mainly by the flow rate of the incoming CO2.